During a marathon, you need 60 to 90 grams of simple carbohydrates per hour, taken in small amounts every 15 to 20 minutes, along with fluids and sodium. Your body can only store enough glycogen to fuel roughly 90 minutes of hard running, so everything after that depends on what you take in. Getting your mid-race nutrition right can be the difference between a strong finish and hitting the wall.
How Many Carbs You Actually Need
The target depends on how long you’ll be out there. For a marathon finished in under two hours (elite territory), 30 grams of carbohydrates per hour is sufficient. Most marathon runners fall in the two- to three-hour range, where the recommendation jumps to 60 grams per hour. If you’re running for three hours or more, the target is 90 grams per hour.
Those numbers sound high, and they are. A single energy gel typically contains 20 to 25 grams of carbs, so hitting 60 grams per hour means consuming two to three gels every hour, or combining gels with sports drinks and other foods. The key is starting early. Begin fueling 30 to 45 minutes into the race rather than waiting until you feel depleted. By the time you feel low on energy, you’re already behind.
Why the Type of Sugar Matters
Your gut can only absorb about 60 to 70 grams of glucose per hour through one set of transporters. To get above that ceiling, you need to add fructose, which uses a separate absorption pathway. This is why many sports nutrition products use a blend of glucose (or maltodextrin) and fructose rather than just one sugar.
If you’re targeting 90 grams per hour, a 2:1 ratio of glucose to fructose works well. If you’re pushing closer to 110 grams per hour (something increasingly common among competitive runners), shifting toward a nearly equal ratio, around 1:0.8, improves absorption. The practical takeaway: check the ingredient label on your gels or drink mix. Products listing both maltodextrin (or glucose) and fructose are designed for this dual-transport approach. Products with only one sugar source will cap out around 60 grams per hour no matter how much you consume.
Real Food Alternatives to Gels
Not everyone tolerates gels, and you don’t have to rely on them. Plenty of whole foods deliver similar carbs in portable form:
- Bananas: about 30 grams of carbs each, easy to grab at aid stations
- Raisins: a handful delivers around 33 grams of carbs and fits in a small bag
- Dates: 20 to 30 grams of carbs per serving, easy to digest
- Pretzels: about 25 to 30 small pretzels give you 30 grams of carbs plus a bit of sodium
- Honey: one tablespoon has 17 grams of simple carbs that absorb quickly (honey packets or straws work well)
- Gummy candy: jelly beans, gummy fish, and marshmallows are high in simple carbs and absorb easily
The trade-off with whole foods is portability and speed. Gels are designed to be consumed in seconds without chewing. A banana takes longer to eat and carry. Many runners use a mix: gels or chews as the backbone of their plan, with real food at aid stations for variety and to settle the stomach.
Sodium and Fluid Intake
Carbs get the most attention, but sodium loss can quietly wreck your race. Marathon runners lose 700 to 1,000 milligrams of sodium per hour through sweat. If you’re running in heat, sweating heavily, or you notice white salt residue on your skin or clothes after long runs, aim for the upper end of that range. Cooler weather and lower intensity bring you closer to 700 milligrams.
Most standard sports drinks contain 200 to 400 milligrams of sodium per serving, which means they won’t fully replace what you lose. Salt tablets, electrolyte capsules, or higher-sodium drink mixes can fill the gap. Pretzels at aid stations also contribute. Sodium isn’t just about preventing cramps. It helps your body absorb and retain the fluid you’re drinking rather than sending it straight through.
For fluid itself, a practical guideline is three or four long sips of water every 15 minutes. Avoid gulping large volumes at once, which increases the chance of stomach sloshing and nausea. Small, frequent sips keep you hydrated without overwhelming your gut. If you’re using a concentrated carbohydrate drink, chase it with plain water to help dilute it in your stomach and speed absorption.
Caffeine as a Late-Race Boost
Caffeine is one of the most well-supported performance aids in endurance sports, and timing it strategically makes a real difference. Rather than loading up before the start, the more effective approach is taking a smaller dose when fatigue sets in, typically in the second half of the race.
A dose of about 3 milligrams per kilogram of body weight is the sweet spot for most runners. For a 70-kilogram (154-pound) runner, that’s roughly 200 milligrams, equivalent to a strong cup of coffee. Many caffeinated gels contain 25 to 50 milligrams each, so you can spread your intake across the later miles. The goal is to find the lowest dose that noticeably helps, since higher amounts increase the risk of GI distress, jitteriness, and a racing heart rate that’s counterproductive.
Avoiding Stomach Problems
Gut distress is one of the most common reasons runners slow down or drop out of marathons, and it’s almost always linked to nutrition choices. Highly concentrated sugar solutions sit in your stomach longer and can pull water into your intestines, causing bloating, cramping, and diarrhea. Taking gels without enough water is a frequent culprit. Fat, fiber, and protein also slow digestion, which is why race-day fuel should be almost entirely simple carbohydrates.
The single most effective thing you can do to prevent stomach problems is train your gut in the months before race day. Your intestines physically adapt to handling more carbohydrates during exercise. Eating a high-carbohydrate diet for as little as two weeks can double the number of sugar transporters in your intestinal lining, dramatically improving how much fuel you can absorb without distress. Practicing your race nutrition plan at least once a week during training runs lets your digestive system adapt over six to ten weeks. Even a few days of dietary changes can speed up how quickly your stomach empties during exercise.
This means your long training runs aren’t just for building fitness. They’re rehearsals for your fueling plan. Use the same gels, drinks, and foods you plan to use on race day, at the same intervals, at race pace. If something causes problems in training, you have time to switch products or adjust timing. Discovering a gel doesn’t agree with you at mile 18 of the actual race is a problem you can entirely avoid.
Putting Together a Race-Day Plan
A practical fueling schedule for a runner targeting a 3.5- to 4-hour marathon might look like this: start with a gel or a few chews at 30 to 40 minutes in, then take in another 20 to 25 grams of carbs every 20 minutes after that. Sip water at every aid station. Add an electrolyte source (salt capsule, salted chews, or a sodium-rich drink) every 30 to 45 minutes. Save caffeinated gels for miles 16 to 20 onward, when fatigue typically peaks.
Carry your fuel in a running belt, shorts pockets, or handheld bottle rather than relying entirely on aid stations, which may not have what you need or may be crowded. Pre-open gel packets and store them in accessible spots so you’re not fumbling with wrappers while running. And keep a simple rule: if you’re on schedule, stay on schedule. Skipping a fueling window because you feel fine in the moment often catches up with you six or eight miles later when glycogen stores bottom out.